Migration from circuit switched (CS) based networks to packet switched (PS) based networks (e.g., IMS based networks) will be done in steps, and the two networks may co-exist for a long time. A number of solutions have been standardized over the last years for enabling migration towards an IMS based infrastructure, such as, for example Voice Call Continuity (VCC). Most of these solutions allow a CS bearer to be used to carry speech traffic for a user, while providing the service control in IMS. The solutions may also allow the user to transfer traffic between CS bearers and PS bearers. With respect to media security, it is desired to provide a means for providing end-to-end media security in the case where the media traffic travels across both a CS network and a PS network.